This invention relates generally to flow passage coupling units and, more particularly, to a flow passage coupling unit for coupling the first passage of the first member and the second passage of the second member.
A conventional flow passage coupling unit such as disclosed in Japanese U.M. Patent Application Kokai No. 60-167,888 is shown in FIG. 4. This flow passage coupling unit includes a coupling unit 53 which consists of a cylindrical body 51 secured to a movable body 50 to which a tube may be connected. A fixed body 55 with a passage 54' is opposed to the coupling unit 53. The cylindrical body 51 has a large bore 56 communicating with a passage 54 of the movable body 50 and a small bore 57 in which a sliding valve 52 fits. A valve seat 58 is made of a conical surface between the large and small bores 56 and 57.
The sliding valve 52 has an axial passage 59 extending in the axial direction and a through-hole 60 through the sliding surface of the sliding valve. A seal ring 61 is mounted on the front end of the sliding valve. The sliding valve 52 has on the rear end a valve head 63 with a conical surface 62 which rests on the valve seat 58. A coil spring 64 forwardly biases the sliding valve 52.
In operation, the movable body 50 is moved forwardly so that the seal ring 61 of the sliding valve 52 abuts the coupling surface 65 of the fixed body 55. When the movable body 50 is further moved forwardly, the sliding valve 52 is moved backwardly with respect to the cylindrical body 51 against the bias of the spring 64. Consequently, the valve head 63 is moved away from the valve seat 58 to couple the passage 54 of the movable body 50 to the passage 54' of the fixed body 55 through the large bore 56, the through-hole 60, and the axial passage 59.
However, the valve head 63 and the valve seat 62 of the above flow passage coupling unit are made of conical surfaces so that the increasing rate of opening space between the valve head 63 and the valve seat 62 is not so high as the moving rate of the sliding valve 52. Consequently, in order to provide the desired area of the opening space, it is necessary to move the sliding valve 52 to a large extent, resulting in the large unit size.